I perfer to err on the side of leaving 30-minutes or there about. It's pretty easy to do. Turn the kettle on. Get sidetracked with something or another, kids and dogs ar handy for that. Turn the kettle back on and if I drink it 20 minutes after SFQ I don't worry about it. I'm just not perfect in that way
The thing is that the digestive system has to work whenever you put something into it. That takes away energy in part from the blockages you've been working on. 30 minutes is roughly the bodies cycle for natural completion and winding down after exercises. So don't rush it getting something into the system. Start SFQ 10 minutes earlier if you need a drink before you leave.
Alex