1. I suppose this was supposed to be "wanna", slang for "want to"? Tacky.
2. How does one treat someone? One treats them well. "Well" should be used as it is an adverb modifying the word "treat".
3. If one does indeed want to treat her well, he should buy her
an ICEE. "An" should be used instead of "a" before nouns which begin with a vowel.
To see more misspelled signs, click HERE.