A 68 year old man is reviewed in the cardiology outpatient clinic following a recent admission with worsening heart failure. He reports feeling much less breathless since discharge but still becomes short of breath when walking uphill. PMH. Heart failure with reduced ejection fraction, chronic kidney disease stage 2, hypertension. DH. Bisoprolol 5 mg PO once daily, ramipril 5 mg PO once daily, furosemide 40 mg PO once daily, spironolactone 25 mg PO once daily.

On examination
BP 126/74 mmHg, HR 68 beats/min, weight 86 kg.

Investigations
Sodium 140 mmol/L (135-145)
Potassium 4.5 mmol/L (3.5-5.5)
eGFR 74 mL/min/1.73 m² (>60)
HbA1c 40 mmol/mol (20-42)

To optimise his heart failure treatment, the cardiologist starts empagliflozin 10 mg PO once daily.

Select the most likely adverse effect associated with the new treatment.