Ibotta - $1 off one 750 mL bottle (https://ibotta.com/rebates/23260/...26-spirits)
Checkout 51 - $1 off one 750 mL bottle (limit 1) (see attached screenshot)
Snap by Groupon - $1 off one 750 mL bottle (no limit) https://snap.groupon.co
Shopmium - $1 off one 750 mL bottle or $2.50 off two 750 mL bottles (see attached screenshots)
YMMV depending on your state, looks like these expire around September 13th or so. All usually require an itemized receipt (showing the product name for each line item) and to scan the barcode on the bottle. Not the best champagne by any means, but for cheap mimosas it's not so bad.