How to check if a string has a certain text with a script?

[scavengingbot]

i am making a glass bottle to pickup water and the script i used to pickup water actually works it changes the tooltip from empty to full.
the issue:
now that i want to check if the tooltip is indeed full (with a scipt)
it doesn’t work.
script in question

script.Parent.Touched:Connect(function(hit)
	local plr = game.Players:GetPlayerFromCharacter(hit.Parent)
	if plr.Backpack:FindFirstChild("bottle").ToolTip == "Full" then
		script.Parent:Destroy()
	end
end)

im probably doing it wrong but i want to know how to really check if a string has a certain text
(if there is even a way to check that)
(for if you haven’t noticed yet i am a beginner)

[Valkyrop (JustAGuy)]

Is the bottle located in the backpack when it happens?
Also, what are you trying to compare/check here?

[calvin_coco (where)]

if plr.Backpack:FindFirstChild("bottle").ToolTip:find("Full") then -- find the string pattern "Full" in the ToolTip

[ExercitusMortem (Exercitus)]

script.Parent.Touched:Connect(function(hit)
-- Is hit.Parent always a Character? Doesn't have to be. How about change it to a clickdetector? That's more efficient, because it won't run this everytime anything touches it.
	local plr = game.Players:GetPlayerFromCharacter(hit.Parent)
-- I'd seperate looking for the bottle and checking the tooltip first.
	if plr.Backpack:FindFirstChild("bottle").ToolTip == "Full" then
-- You're checking if the bottle is full. If so, you'll remove script.Parent (which I assume is the water). This is the wrong way around, as you'd more likely need to check if it's empty before adding new water. If it's full, do nothing. I assume this is the reason why your code isn't working, btw.
		script.Parent:Destroy()
	end
end)

A better way to do it would be this:

script.Parent.ClickDetector.MouseClick:connect(function(plr) -- Run this when clicked
	if plr.Backpack:FindFirstChild("bottle") == nil  then -- Check if player has bottle
		warn("no bottle")								
	else
		
		if plr.Backpack["bottle"].ToolTip ~= "Full" then	-- Check if bottle is full
			warn("bottle already full")	
		else
			script.Parent:Destroy()						-- Destroy water
			plr.Backpack["bottle"].ToolTip = "Full"		-- Set ToolTip to full
		end
	end
end)

It would actually be even better if you approach this from the tool itself.

Inside a localscript, in the tool:

local player = game.Players.LocalPlayer
local mouse = player:GetMouse()

script.Parent.Activated:Connect(function()
	if mouse.Target == nil or mouse.Target.Name ~= "water" then -- Check if the mouse is on valid target
		warn("Wrong target.")
	else
		if script.Parent.ToolTip == "Full" then	-- Check if full
			warn("Bottle full")
		else
			print("Succes!")
			game.ReplicatedStorage:WaitForChild("waterEvent"):FireServer(script.Parent, mouse.Target) -- Tell the server you're picking up the water.
		end
	end
end)

In a server, in ServerScriptService

local waterEvent = Instance.new("RemoteEvent", game.ReplicatedStorage) -- Create a new remote event
waterEvent.Name = "waterEvent"

waterEvent.OnServerEvent:Connect(function(Player,bottle,waterPart)
	waterPart:Destroy()
	bottle.ToolTip = "Full"
	bottle.Enabled = false
end)

[scavengingbot]

yes it has to be located in the backpack.
im trying to make a door that only opens if the bottle is full
so im checking if it is by checking if the tooltip says full instead of empty