S Corporation paid for potential client vacation tax deduction?

you can only claim client gifts of $25. the vacation is over the top and can't be fully deducted

No.

Travel expense refers to expenses incurred by the taxpayer, not a potential client, while away from home.

Entertainment must be ordinary and necessary to the conduct of your business. It would be difficult to show that a 5-day tourist vacation, as you describe, is an accepted business expense for your business activity.

Read IRS Pub 463 for more details on travel and entertainment expense.

You need to be able to prove a valid business reason for the expenses. They seem a bit excessive. Did the trip result in a successful business deal? That would help. The IRS loves to audit and disallow these kinds of expenses. It's one thing if you spent $10,000 to secure a $1,000,000 contract. Completely another if you spent that kind of money on a $50,000 contract. Your only other option is to take it as a shareholder distribution.

And the question is what?

I have a S Corporation, and I have paid for a 5 day tourist trip for three of my potential clients. They are foreigners and I also paid for their hotels while they staying in my area. Are these all can be treated as entertainment or travel expenses on my form 1120S for tax deduction?

Must issue 1099-Misc for "prize."