There's some real evidence suggesting that eating less, for example by skipping breakfast, will slightly increase your odds of a girl:
https://www.reuters.com/article/us-gender-diet/skipping-breakfast-may-mean-your-baby-is-a-girl-idUSL2284780520080423
"Mathews and colleagues studied 740 first-time pregnant mothers in Britain and found 56 percent of those in the group with the highest energy intake at conception had sons, compared with 45 percent in the lowest group. ...In humans, going without breakfast may be interpreted by the body as signaling low food availability, since it depresses levels of blood sugar."
Obviously this is far from definitive, and even if it is right, it's just shifts the odds a bit, but worth trying.
Oh, and one more data point: I skipped breakfast regularly and followed up 2 boys with a girl.