I'm not a fan of manufactured spending, personally, and I think it will ultimately hurt those of us who want to profit from these bonuses, because they'll shut down the programs. But what I do to hit the spending targets is:
Go on trips paid for by work, and put the airfare, hotel etc. on the credit card, which will be reimbursed. (Obviously not possible unless you travel for work.)
When I go out to eat or to an event, I pay for everyone in my group with the credit card, and they give me cash.
Any major expenditures (house repairs, trips, etc.) are calculated carefully to match up with credit card bonus spends.