This is generally solved with a note alongside the cash.
"Please treat yourself to a meal at my favourite restaurant, X."
"I think you can buy some plants for the garden."
"Please treat yourself to a meal at my favourite restaurant, X."
"I think you can buy some plants for the garden."
I think "solved" here should be "mitigated". Certainly culturally it seems lots of people don't consider this equivalent although logically it could be seen as "better".
If you do something like that, you are making your gift conditional.