To offer free tasting for all potential customer這句句子是不是沒有動詞

To offer free tasting for all potential customer – correct in grammar
In this sentence :
offer is the verb
to offer is a phrasal verb = preposition + verb = a verb with special meaning
For example :
I would like to offer you some drinks. Here offer is the verb, just like : I would like to do something, do is the verb.

"To offer" is used as infinitive subject . The sentence "To see is believe" is wrong. It should be changed to "To see is to believe.

你說得一點沒有錯，這句並不是完整句子，而to offer明顯是to-不定詞（to-infinitive)，所以這句並沒有主動詞，只能說是片語(phrase)用作名詞片語(noun phrase)，或用作表示條件的副詞不定詞的獨立不定詞，但沒有全句，所以暫不能確定：
如：To deceive him is easy.的to deceive就是名詞不定詞
如：To be plain with you, he is a liar. to be plain就是副詞不定詞，作獨立不定詞(Absolute Infinitive）用
所以你的句子，若像 ：
To offer free tasting for all potential customer(s) is ...，則用作名詞不定詞
但若句子像
To offer free tasting for all potential customer(s), We must ...

希望幫到你！